Xilman

I was not aware of that thread.

Not all eyepieces and Barlows are as achromatic as perhaps they ought to be ...

One possibility is an equatorial platform. Not only does an eq platform make visual observing markedly easier, it makes imaging possible. https://www.skyatnightmagazine.com/advice/build-a-dobsonian-equatorial-platform shows you how to make one. Finding how to buy one is left as an exercise in the use of search engine as I do not wish to promote any particular supplier. Some people, Martin Lewis in particular, take absolutely superb images with a Dobsonian. He often shows surface detail on the Galilean satellites of Jupiter, for instance. His web site is https://skyinspector.co.uk/ and a representative set of images can be found at https://skyinspector.co.uk/jupiter/#bwg5/1257

Welcome aboard. Remember: there are very very few stupid questions. Unfortunately there are stupìd answers given every now and again but we try to keep them to a minimum and to take corrective action if one should sneak through.

Welcome aboard. I am technically in Spain right now, but not in the Peninsular. La Palma to be precise.

What looks like a few background galaxies too. For example, the bright spot in blue streak in the spiral arm (itself a HII region) at the 10 o'clock position is the galaxy LAMOST J120312.23+443001.8 and the bright orange streak in the upper left corner is NGC 4013, a 12.4 magnitude edge-on spiral.

Might be clear here later. Roughly 50% cloud cover but very windy. Wind generally makes for lousy seeing, sometimes as bad as 20 arcsec!

Note that slight trailing will happen if the polar alignment isn't good enough ... (Edit: ssorry, I didn't spot this point had already been made.)

Geckos eat spiders ...

Advice which goes back many decades but, sadly, which many people don't receive until after they have spent their budget is as follows. Spend as much on the mount as you do on the telescope which is attached to it. Only Dobsonian owners can get away with ignoring this rule. Professionals have another rule: the observatory building costs as much as the telescope or the mount.

Two things: Is the motor running too fast or too slow? If so then even if the system is perfectly balanced the stars will still be trailed. If you add more weight to one side, does the direction of drift change? If so, you will need to add or subtract ever smaller weights until the drift is acceptable. A common way of dealing with drift, and I've used it myself quite often, is to take subs with an exposure short enough that the drift is small enough and then stack the subs. Very occasionally, I deconvolve an image using a PSF taken from one or more trailed star images. This is very much second best, in my experience.

Cobwebs happen. Live with it. A feather duster will remove any which are in the light path. Over here in La Palma we are much more concerned about gecko droppings, which gets everywhere and is far more damaging than cobwebs. It is essential to keep optical surfaces covered when not in use. Sorry to be blunt, but that's life. 😉

Now there's a challenge. It should be possible to amateur spectroscopists to measure radial velocities of bright stars in different spiral arms. A hundred or few carefully selected stars should be sufficient. Accepted: it is much easier for radio astronomers.

Some optical astronomers are not affected much about daylight either, though clouds are still a PITA. Solar work has to be done in daytime. It is very common for planetary observers of Mercury through Saturn to sketch or image in daylight, as do lunar observers of course. Bright stars are easily visible telescopically in full daylight, especially through a near-IR filter. One item on my bucket list, and it has been there for years now, is to image as many Messier objects as possible while the Sun is above the horizon. M45 should be trivial. I have high hopes of M13, M36, M37, M92, ... The main problem is finding them, though offsetting from the Moon, Sun or Venus may be a solution. So don´t come over all superior. You are allowed to sneer about how clouds cripple us. 😉

There are quite a few variable stars in Messier 5, though few people seem to go looking for them. This image shows V42, a RV Tauri type of pulsating variable. It was close to maximum brightness when the image was taken on 2021-07-02. Those of you who like imaging M5 may wish to monitor how the VS changes the appearance of the cluster over time. Even if you prefer to use a Mark-1 eyeball the star's varying brightness is fairly easy to follow as it is around 11th magnitude. 35 seconds on an unfiltered SX 814 camera attached to a 0.4m Dilworth reflector.

It is not clear from your description whether you are taking separate flats for each filter you use. I hope you are, because each filter will have its own distribution of crud on its surfaces. Ideally you should take flats before each observing session so that changes in dust distribution are accounted for. Twilight flats are generally used for this approach, though dome flats are also a possibility. In my experience, very few people are this fastidious --- I am certainly not, but I have a very stable set up with a fully enclosed optical train mounted in an observatory so I can get away with re-using flats for a period of a few weeks.

It started as a discussion about noise in images. I provided a link to my experiments with FABADA, which can do quite amazing things with noise in images. The discussion all rather snowballed from there, sorry. If a moderator wishes to move some of this thread elsewhere, somewhere more suitable, I would be quite happy with that. As for equipment, all I have used is the fabada software. The data was provided by @alacant so I can't say anything meaningful about how it was taken. Paul

OK, I sussed it. The code as written can not handle anything bu 1D (spectra, etc) or 2D (monochrome image) data. A colour image is 3D data, the third dimension being the colour channels. So what I did was to separate out each channel in your image, smooth them separately, and re-combine into a tri-colour smoothed image. Added in edit: I contacted Pablo about this issue.

That is a new one on me. What is the alleged size of the image? Do the FITS headers agree with the data which follows? I would hope so or something is very seriously wrong. Is it a colour image? I only ever process monochrome images so there is only ever one HDU. If so, you may need to specify each plane separately and re-merge the three after smoothing. If this is the case, use the -hdu option setting its value (presumably) to 0, 1 and 2 in turn. If you still can't get it to work, I suggest contacting the author for assistance. Good luck!

I call it as "fabada -out smooth.fits raw.fits 100" for an appropriate value of 100. The noise value is chosen by experiment! Too small and no smoothing is done. Too little and artefacts appear. I am sure that there must be a better way but I have not yet found it. What sort of error do you get? There may be a bug in the code. I found a couple when it was first released but the author is very responsive and within 2 days he told me that he'd fixed them. As I had already implemented my own fixes I didn't bother downloading a fresh copy.

I have two 150mm (6 inch) refractors from which I may be persuaded to part. No mount, just the OTA,

My favourite telescope porn can be found at https://planewave.com/product/pw1000-observatory-system-rc-optical-design/ If I had a megabuck to spare I would buy one like a shot.

I see you are using Ubuntu (like me) so you may wish to investigate FABADA. It can be quite spectacular when it comes to noise reduction so perhaps you could continue taking longer exposures.

Doubleplus ungood. 8-( Only two ornaments are visible. Do you have all three? Earache, headache and toothache that is. Now hoping my Meade out in La Palma is not in a similar condition.

A 120mm refractor makes a very good guider. 😉 That's what mine is used for mostly. It is also far far better for solar work than the 400mm for which it acts as a guider most of the time. Solar heating would destroy that one.